54 BRAIN MECHANISMS AND LEARNING 



young as 14 days) they were kept isolated in wiremesh cages and fed only 

 with powdered food. After they had mated he put them in a wooden box 

 with strips of paper hanging from the walls. Nest building and retrieving 

 were looked for in this testbox, but the animals failed to build nests and to 

 retrieve their babies. They only carried the young around and scattered 

 the paper strips all over the floor. Most of the nestlings died, as they were 

 not sufficiently cared for by their mother. From this failure to build nests 

 and to retrieve, Riess concluded that the nest-building behaviour of the 

 rat must be learned during ontogeny through handling solid objects. One 

 could not apply the term instinct, therefore, to this type of behaviour. 

 The way in which the rat might learn nest building was pointed out by 

 Lehrmami (1954). The rat might collect food and other objects at its 

 sleeping place and thereby observe that some of these collected objects 

 can be used to prevent loss of heat. It would in this way learn to build a 

 nest as soon as it felt cold. No attempt was made to gain detailed observa- 

 tional information concerning either recurring motor patterns or the 

 stimulus situations indispensable to elicit them. 



From observing a small number of different rodents [Miis iiiiisaihis L., 

 Rattiis uorve^iais L., Merioiies persiciis Blanf., Meriones shawi, GerbiUus 

 gerhilhis L., Jaciihis jaciihis L., Cricctiis cricetus L., Mesocrketus aiiratiis 

 Waterhouse, Mkrotus arvalis Pall., CitclUis citeUiis L., Glaiicoiuyys t'ohms 

 Thomas, Sciiinis i'iiJ(^ciris L., Glis glis L., Muscardiinis avellaiiariiis L., 

 Dasyprocta aguti, Oryctolagiis ciiiiiciihis L.) I was familiar with a number of 

 motor patterns recurring in most or all of them (Eibl-Eibesfeldt, 1958). 



In all ground-dwelling rodents observed, two phases of nest building 

 can be distinguished: (i) The digging of a burrow (2) the construction of a 

 nest for sleeping and nursing. 



The nest-building Norway rat for example starts digging a tunnel, 

 20 to 30 cm. under the surface, which ends after about i metre in a small 

 nesting chamber. Later, additional tunnels are added (Steiniger, 1950). The 

 forelegs scratch the earth with alternating movements from the front 

 under the belly [scratchiiiii). From there the accumulating earth is pushed 

 backwards by the hindlegs {kicking backwards). From time to time the 

 animal turns around pushing the earth by alternating movements of its 

 forelegs out of the tunnel (piisliiiig). Pushing with the snout is also observed. 

 After digging the animal collects nesting material. This collection activity 

 consists in grasping the nesting material with the teeth, piillitig it free and 

 if necessary biting it loose from where it is attached, then carrying it to the 

 nesting site and depositing it there. 



The nesting material is pushed into a heap by movements of the fore- 



